Prior to the instant invention several techniques have been employed to provide extendable, retractable covering for planar surfaces. Analogous art was concerned with providing movable covers over openings ranging from the common window to missile silo emplacements. Covers ranged from the opaque or translucent conventional window shading to a multiplicity of interlocked slats or meta*/concrete segments. The nonmanual motivation, in turn, was just as varied; the heavier and more cumbersome shading/covering often requiring heavy, cumbersome machinery which motivated it, usually through pulley and cable mechanisms. In instances where the motivation comprised a direct drive or geared motor/traction mechanism, the motor was invariably fixed and the driving gear train either engaged portions of the cover or, as was more often the case, drove a pulley system or a capstan to either take up or play out a drive cable.
More notably the window shading art has begun to develop materials particular to the needs of those seeking insulative shading, particularly in the home or in such environment as the common greenhouse. To this end, there have been recent developments in insulative shading materials and apparatus. Patents issued to Rasmussen (U.S. Pat. No. 4,019,554) and Colson (U.S. Pat. No. 4,603,072) are indicative of such interest and portray a state-of-the-art benchmark for the instant invention. Rasmussen developed a thermal insulating curtain for use especially in greenhouses by adapting the slat array of the common Venetian Blind with parallel interconnecting foldable fabric nettings to obtain the result of a rectalinear curtain comprised of two fabric surfaces seemingly partitioned by a slat array. It is intuitive that the slat elements comprising the partitions of the curtain were rigid enough to allow the curtain to rest extended on a horizontal surface. Absent rigidity of the slats however, the Rasmussen invention could only function in a vertical suspension mode. Colson on the other hand, developed a honeycomb, insulating shade comprised of continuous thin film plastic material which effected a series of concatinated flexible tubular elements. Like The Rasmussen invention however, Colson's in order to be used on a horizontal planar surface would have to rest on the margins or frame of a window or else be used with supporting battens.
Typical of the motorized drives employed with current greenhouse and solar shade apparata is the arrangement disclosed in the patent issued to Esposito (U.S. Pat. No. 4,606,157) wherein a shade is provided for being drawn across greenhouse glazing by action of a motor driven roller connected at one end of the shade and used to play out or wind up the shade. In the Esposito arrangement, the other end of the shade is connected to a device which applies a constant retracting force that is used to maintain tautness in the shade. The shade is played out and taken up by running between a pair of parallel tracks which have inward facing grooves. The outer margins of the shade contain a filament which lends a bulbous character to the shade margins. These margins are effectively captured in the grooves of the parallel tracks.
Not withstanding the aforesaid advancements to the art, there yet remain onerous problems to effectively shading glazed surfaces and particularly vertical and horizontal windows. Some of the most bothersome involve nonmanual drive mechanisms which have heretofore embodied cord, cable and pulley drive mechanisms, do not effect good environmental seals, and, when used in any position substantially off the vertical, tend to sag.
It is therefore an object of this invention to provide a shade drive mechanism that operates without the encumbrances of pulleys, cords or cables.
It is a concomitant object of the invention to provide a system having a discrete, resident drive means for each shade unit.
It is yet another object of this invention to provide a means for disengagement of the invention's resident drive means and for stabilizing or braking shade travel.
It is yet another object of the invention to provide a form of electrical energization to the resident drive means.
It is yet another object of this invention to provide a shade which may be moved and stopped by manual manipulation of the resident drive mechanism for movement and securement at any point between the closed and open positions.
Other objects are set forth hereinafter or shall become apparent from practice with the invention or similar embodiments the same being practiced within the bounds of the appended claims.